function y=gafit(x0)

% this function is the sum inside the mean squared error between
% the gaussfit data and a Gaussian with parameter
% vector x0

load gaussfit.dat
x=gaussfit(:,1);
y=gaussfit(:,2);

sum1=0;
for j=1:length(x)
   sum1=sum1+ ( x0(1)*exp(-x0(2)*x(j)^2)-y(j))^2;
end
y=sum1;